set between (Everything Changes) and (Glade) of 'Friends From Unexpected Places'
Mirror's Edge has been in Ponyville for a few months, being cared for by Fluttershy after being critically injured. he's become a part of the town and a part of Fluttershy's life, even feeling something he never felt before. after F.S. and her friends are invited to attend the wedding of Trixie and Luna, he feels that he's now a part of the whole world and not just a random member of the swarm.
while there, however... he, Twilight, and Requiem discover a plot that Chrysalis and the Changelings are returning. now, Edge must choose between helping his own kind or helping the ponies he loves as the second Battle for Canterlot begins.
(yes, i am aware that there is a Fanfic out there with a Changeling named Mirror's Edge. it is purely coincidental. i choose the name because it fits with the Changeling's nature. plus, i like the game: http://www.youtube.com/watch?v=TERyxFfMqDk )